System Design
April 2020 3-4 06-237619-001
3-3 EXTINGUISHING VALUES
When calculating the required quantity of the selected Agent to be stored, use the most
demanding flammable material involved and the net volume of the protected enclosure/room.
The resulting oxygen concentration after release shall be calculated based on the net volume
and the total quantity of Agent released.
The values listed below are all based on fire extinguishing tests at 20°C:
The extinguishing concentration required is independent of the temperature. However, the
quantity (in kg/m
3
) needed to reach the required concentration is dependent on the
temperature. i.e. the quantity (kg/m
3
) needed reduces at higher temperatures.
Noted that for systems having a relatively large distribution piping system, additional gas may
be required. For systems with relatively short pipe work any such supplement may not be
needed.
Note: The actual minimum required stored Agent quantity can only be verified using the flow
calculation software. Consult the flow calculations software for the specific Agent used.
3-4 DISCHARGE TIME
The discharge time required to achieve 95 percent of the minimum design concentration for
flame extinguishment based on a 20 percent safety factor shall not exceed 60 seconds for Class
B fires, 120 seconds for Class A surface fire hazards or Class C hazards, or as otherwise
required by the authority having jurisdiction.
3-5 MINIMUM DESIGN CONCENTRATIONS (MDC’S)
The residual oxygen level (ROL) of the hazard area after a discharge shall always be within the
project/safety regulations (NOAEL 43% / LOAEL 52%)
Abbreviations used in table below:
EC = Extinguishing Concentration
SF = Safety Factor
MDC = Minimum Design Concentration
MDQ = Minimum Design Quantity
ROL = Residual O2 Level (Concentration)
Values calculated at 20 degree Celsius and atmospheric pressure 1.013 bar. For certain Class
B fuels, should the MEC be below the heptane, the value for heptane shall be used to calculate
the MDC.
Table 3-1. Design Concentrations for IG-01 and IG-55
Fuel
IG-100 IG-55
Minimum design
% by volume
Minimum design
% by volume
Class B (Heptane) 44.0 47.8
Class A 42.1 42.5
Class C 47.4 47.8
WARNING
Should the required agent quantity cause the oxygen level of the room to drop
below 12%, it is not safe for the room to be occupied and steps must be taken
to ensure the area is vacated immediately.
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